Korean Job Discussion Forums

[yesterday's child]

[sonofthedarkstranger]

Its existence was a given, and there are many, many more.

[VanIslander]

By a more accurate definition, there are only eight planets in our solar system.

"Pluto is not really a planet."

It's conceptually misleading to use the same term for quite different things.

Pluto is an asteroid. Or the new scientific classification: "Trans-Neptunian Object."

There are thousands of objects like Pluto in the outer realms of this solar system.

Only tradition keeps us from calling a spade a spade.

We like to think of Pluto as a planet because that's what we've been thinking for a long time.

http://news.bbc.co.uk/1/hi/sci/tech/259767.stm

[skinhead]

What defines the edge of our solar system? Is there a common border with the next? Mithridates, your expertise is requested. Astronomy ~ if I could go back in time I'd do physics at school rather than DRAMA, then pursue the elemental path of astrophysics and follow Andy Thomas up and out of the bubble. sigh...

While on it, has anyone seen the BBC production called 'Space Odyssey'? Charming little CG romp through the SS. Pluto is now my favourite iced rock. Come the space tourism era and my fat pension, I'm there baby.

[mithridates]

The edge of the solar system is way farther out than we thought. The Oort cloud might extend out over a light year, which is a quarter of the way to the next star system.

All right, check this out:



See, each picture zooms out into the next. That red orbit is Sedna, which extends to about 30 times that of Pluto's orbit, but it's still nowhere near the Oort Cloud. It's actually a bit weird that it extends out that far though because the Kuiper Belt is supposed to drop off pretty soon after Pluto, but it goes out much farther than that.

[sonofthedarkstranger]

[Tiberious aka Sparkles]

[yesterday's child]

[VanIslander]

Uh, no.

Either there are 8 planets or else there are 100s or 1000s in our solar system.

It's a question of definition.

If Pluto is a deemed planet, then our solar system has thousands of planets (unless size becomes a determining factor, then only maybe dozens or hundreds).

But Pluto shouldn't be considered a planet many scientists say. Only tradition makes us want to say so. It's what has come to be called a "Trans-Neptunian Object".

Pluto is basically a big rock with a nitrogen compound on it, quite unlike the eight planets and very much like the large outer asteroids.

For about half of the year it has NO atmosphere, is basically an asteroid with frozen gas, more like the supposed tenth planet.

For about the other half of the year the frozen nitrogen compound melts by the heat of the sun and creates a temporary atmosphere of sorts (which those desperate to hold onto the old notion of Pluto as a planet cling to, even though this minimal atmosphere is hardly that, and only for part of the year).

Realistically, there are eight planets in our solar system and a bunch of rocks outside of that.

But it's more romantic to think about the possibility of a tenth, eleventh, twelfth planet, and the idea of multiplicity, of possible worlds we may explore or inhabit.

To use the word "planet" so loosely is misleading in the extreme. Hence, the attractiveness of the so-called "tenth planet" story.

[Tiberious aka Sparkles]

[mithridates]

There was another object discovered that was announced just a day or two before this one; people thought for a while that they were talking about the same one. This other one seems to be about 50-70% the size of Pluto, and it has its own moon.
There are also asteroids with their own moons.
There are also planets without atmospheres and moons with atmospheres.

The Japanese definition for planet, BTW, is wakusei which means 'confusing star', because they don't follow the same path other stars do. In Korean it's 'moving star'. What's the etymology for English? Let's check.

Ah. Greek planetai - wandering star. Same thing.

What's a planet? The more powerful our telescopes are, the more of these wandering stars we can see. Or maybe we should define them as bodies in the solar system that can be seen with the naked eye? No, that cancels out Neptune.

I don't know. Whatever.

[sonofthedarkstranger]

Hmm. Well, what makes a planet a planet?

You are right VanIslander--it is pretty much a question of semantics.

Is Pluto "not a planet" because it is so small? Or because there seem to be many objects just like it?

What would it take to make Pluto a planet?

Would it need to be bigger? If so, how much bigger?

Would it need to have a more regular orbit?

Would there need to be fewer objects that are similar to it?

All of the above? At least two of the above? Any of the above?

----

"trans-Neptunian objects" is a mouthful and moreover there is every reason to believe these things exist in other solar systems too.

In any case, it's hard to say just how interesting this new object is in and of itself--planet or not.

[joe_doufu]

I tend to think of major satellites as planets. Certainly Titan, Europa, Ganymede, etc. are just as deserving of our interest as Mercury and Pluto are. The distinction between "planets" and "moons" is misleading, we shouldn't "rank" celestial objects by where and how they orbit.

I found this link just now: http://www.spacetoday.org/SolSys/Moons/MoonsSolSys.html with a list of moons in the solar system. I'm astonished to find that Jupiter now has 62 known moons, and Uranus has 27 mostly named after Shakespearean characters. That's a helluva lot more than when i was in grade school.

Pluto is interesting because it's a "double planet" system, Charon being almost the size of Pluto itself. Indeed this is also true of the Earth and its moon.

[yesterday's child]

[Tiberious aka Sparkles]